Backfill for engineered barrier

Abstract

A backfill for an engineered barrier used to contain radioactive waste has a predetermined amount of clayic material and a predetermined amount of a reinforcement material with hydrophobic surface characteristics. The reinforcement material may include hydrophobic compounds selected from group consisting of organic polymers or inorganic materials on which a layer of hydrophobic compounds is formed. The hydrophobic reinforcement material results in the backfill maintaining a very low water permeability while providing high mechanical strength and other properties suitable for use in a repository of radioactive waste.

What is claimed is: 
     
       1. A backfill material for use in an engineering barrier, comprising: a clayic material selected from the group consisting of bentonite, montmorillonite, illite, kaolinite, laterite, ectorite, and attapulgite; and   at least one noncementitious reinforcement material, said reinforcement material having a hydrophobic surface.   
     
     
       2. The backfill material according to claim 1, wherein the hydrophobic surface of the reinforcement material comprises an organic surface coating selected from the group consisting of organic titanate, organic silicone, alcohol and esters. 
     
     
       3. The backfill material according to claim 1, wherein the clayic material is bentonite, the reinforcement material is sand, and the hydrophobic surface is a coating of organic titanate. 
     
     
       4. The backfill material according to claim 1, wherein the clayic material is bentonite, the reinforcement material is sand, and the hydrophobic surface is a coating of polyethylene. 
     
     
       5. The backfill material according to claim 1, wherein the clayic material is bentonite, the reinforcement material is sand, and the hydrophobic surface is a coating of asphalt. 
     
     
       6. A backfill material for use in an engineering barrier, comprising a clayic material, and at least one reinforcement material, said reinforcement material having a hydrophobic surface; wherein the hydrophobic surface of the reinforcement material comprises an organic surface coating selected from the group consisting of resins, heavy oils, pitch, and asphalt.   
     
     
       7. A barrier for containing radioactive wastes, comprising a backfill material having a clayic material and at least one reinforcement material, said reinforcement material having a hydrophobic surface for minimizing water permeability of the barrier; wherein said backfill material comprises 5-80% weight composition of said clayic material and 95-20% weight composition of said reinforcement material; and   wherein said hydrophobic surface comprises a coating on said reinforcement material formed of an organic compound, said organic compound being selected from the group consisting of resins, heavy oils, pitch and asphalt.   
     
     
       8. A backfill material in a barrier for containing radioactive wastes, comprising 5-80% weight composition of bentonite and 95-20% weight composition of surface coated sand, said surface coated sand having a hydrophobic surface coating formed of an organic compound. 
     
     
       9. The backfill material according to claim 8, wherein said organic compound is selected from the group consisting of resins, heavy oils, pitch and asphalt.